NASA report: Software, tight budget doomed Mars lander
Illustration of the Polar Lander with descent engines firing
WASHINGTON -- A software flaw probably caused the Mars Polar Lander to shut off its descent engines prematurely, sending it on a fatal plunge into the red planet, according to a report released Tuesday.
So goes the most likely scenario for the demise of the
lander, according to Tom Young, a former Lockheed Martin
executive who presented a NASA blue ribbon report on the fate of the $165 million spacecraft.
| MESSAGE BOARD|
"Spurious signals were generated when the lander legs
deployed during descent," Young said. "It gave a false
indication that the lander (had) landed."
The malfunction would have happened when the lander was about
40 meters, or slightly more than 100 feet, above the surface.
"It would have hit at 22 meters per second, or 50 miles per
hour," he said.
If the lander had come that close to the red planet,
"undoubtedly" this malfunction caused its destruction, Young
told reporters. But no one could know for certain. The design
of the lander prevented any communications as the spacecraft
attempted to land.
Software fix was easy, cheap
Regardless of the cause, Young suggested, similar NASA
missions should require more funding, better training and more
computer program testing.
"There was inadequate software design and testing. The
software should have been designed to prevent premature
engine shutdown," he said. "In space, one strike and you're
There was a full-scale test of the suspect software before
flight, but some touchdown sensors were incorrectly wired,
Young said. After the wiring was corrected, the test was not
Had the defect been known, a software correction
would have been simple and inexpensive, he said.
Microprobes were 'not ready for launch'
Kennedy Space Center technicians lower the Mars Polar Lander onto a workstand in this 1998 file photo
The spacecraft was to have landed near the planet's south
pole to search for signs of water. Two small probes that
ejected from the craft also disappeared. They were supposed
to plunge to the martian surface and analyze subsurface soil
"It is clear that the microprobes were not adequately tested
and were not ready for launch," the Mars Program Independent
Assessment Team report said.
The lander's companion spacecraft, the Mars Climate Orbiter,
was destroyed in September in a mix-up over metric and
Engineers failed to convert numbers in a navigational
program, leading the spacecraft to pass too close to the
planet. Presumably, it burned up in the martian atmosphere.
The two spacecraft cost a total of $320 million.
2001 Mars lander mission canceled
Lockheed Martin technicians working on a 2001 Mars Lander
mission discovered the computer error. "They came to the
conclusion that spurious signals could be present and cause
failure if not compensated for in the software," Young said.
Ed Weiler, NASA's associate administrator, told reporters
that the agency had decided to cancel the planned Mars 2001
Lander mission, which would have deployed a spacecraft nearly identical to the Polar Lander along with a six-wheeled rover.
He said the mission failures were regrettable, but not
entirely unexpected, after NASA, faced with shrinking
budgets, adopted a policy of "faster, better, cheaper,"
almost a decade ago.
"We said up front that this will be painful. We will be
taking risks. We will be pushing the limits. We may lose two
out of every 10 missions," he said.
But Weiler defended NASA's Mars missions, saying most have
been successful and that ones in recent decades have gone
aloft at a fraction of the cost of their predecessors.
Young, a former executive with Lockheed Martin, a primary
NASA contractor, said he did not see a conflict of interest
in his leadership of the review panel.
Conclusion: 'If not ready, do not launch'
He likened the situation to being "a doctor and having a
friend who's sick."
"The worst thing you can do is tell the friend they're really not sick," Young said.
The blue-ribbon panel suggested numerous ways for NASA to
improve performance, including ensuring that future spacecraft can
communicate with mission managers during landing. The doomed
lander was designed to turn its radio antenna away from Earth
temporarily during descent.
Other recommendations include increased involvement from senior
managers and improved communications with contractors.
According to the report, "the final observation that needs to
be made is: If not ready, do not launch."
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Young Report Summary
The Mars Society
Mars Polar Lander
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